Portable gas detectors which can be used to monitor one or more conditions in a region of interest can wirelessly communicate with a Wi-Fi based network of access points. Each of the access points of the network can provide IEEE 802.11 access service. The members of the network can forward detector generated information as to gas concentrations and detector location indicating information to a location manager which can incorporate a location determining engine.
Systems of the type described above have been disclosed in US Patent Application Publication 2011/0161885 published Jun. 30, 2011, application Ser. No. 12/695,736 filed Jan. 28, 2010, entitled “WIRELESS LOCATION-BASED SYSTEM AND METHOD FOR DETECTING HAZARDOUS AND NON-HAZARDOUS CONDITIONS, and US Patent Application Publication 2011/0161044 published Jun. 30, 2011, application Ser. No. 12/959,250 filed Dec. 2, 2010, entitled “WIRELESS LOCATION-BASED SYSTEM FOR DETECTING HAZARDOUS CONDITIONS. The above two published applications, 0161885 and 0161044 are both assigned to the Assignee hereof and are hereby incorporated by reference.
Wi-Fi based wireless location system accuracy is known to exhibit a probability distribution of location error when attempting to estimate the location of a mobile device. For example, the empirical data suggests the average location estimate may be accurate to within 35% of the average wireless local area network (WLAN) access point (AP) spacing when estimated using received signal strength indication (RSSI) information. However some applications may require more accuracy than would be provided by the WLAN infrastructure. Thus in order to provide adequate location system accuracy in a typical WLAN system, it may be necessary to deploy additional access points beyond those necessary for WLAN coverage. Installation of these additional access points may be expensive in terms of material cost of additional APs and also either installation cost of backhaul communications wiring e.g. for Ethernet or material cost of additional radios in the APs to provide equivalent wireless back haul communications. A lower cost solution to improve location accuracy would be desirable.